1. Technical Field
This application relates to UMTS (Universal Mobile Telecommunications System) in general, and to an apparatus and method for making measurements in universal mobile telecommunications system user equipment.
2. Description of the Related Art
The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In a typical cellular radio system, mobile user equipment (UE) communicates via a radio access radio network (RAN) to one or more core networks. User equipment (UE) comprises various types of equipment such as mobile telephones (also known as cellular or cell phones), lap tops with wireless communication capability, personal digital assistants (PDAs) etc. These may be portable, hand held, pocket sized, installed in a vehicle etc and communicate voice and/or data signals with the radio access network.
The radio access network covers a geographical area divided into a plurality of cell areas. Each cell area is served by at least one base station, which may be referred to as a Node B. Each cell is identified by a unique identifier which is broadcast in the cell. The base stations communicate at radio frequencies over an air interface with the UEs within range of the base station. Several base stations may be connected to a radio network controller (RNC) which controls various activities of the base stations. The radio network controllers are typically connected to a core network.
UMTS is a third generation public land mobile telecommunication system. Various standardization bodies are known to publish and set standards for UMTS, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) has been known to publish and set standards for GSM (Global System for Mobile Communications) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) has been known to publish and set standards for CDMA (Code Division Multiple Access) based UMTS. Within the scope of a particular standardization body, specific partners publish and set standards in their respective areas.
Consider a wireless mobile device, generally referred to as user equipment (UE), that complies with the 3GPP specifications for the UMTS protocol. The 3GPP 25.331 specification, v.3.13.0, referred to herein as the 25.331 specification, addresses the subject of the Radio Resource Control (RRC) protocol specification. The 3GPP 25.304 specification, v.3.13.0, referred to herein as the 25.304 specification, addresses the subject of UMTS User Equipment (UE) procedures in idle mode and procedures for cell reselection in connected mode between the UMTS Terrestrial Radio Access Network (UTRAN) and the UE.
Such a UE undertakes frequent measurement procedures. Clause 8.4 of the 25.331 standard and its sub-clauses and clause 14 and its sub-clauses relate to the measurement procedures to be undertaken by the UE as do clause 5 and its sub-clauses of the 25.304 specification. Both the 25.331 standard (and in particular clauses Clause 8.4 and its sub-clauses and clause 14 and its sub-clauses) and the 25.304 standard (and in particular clauses 5.2.3.1 and its sub-clauses) are incorporated herein by reference.
In accordance with clause 5.2.3.1.1 of the 25.304 specification, the UE shall use one of the following two search procedures:
a) Initial Cell Selection
This procedure requires no prior knowledge of which RF channels are UTRA carriers. The UE shall scan all RF channels in the UTRA bands according to its capabilities to find a suitable cell of the selected Public Land Mobile Network (PLMN). On each carrier, the UE need only search for the strongest cell. Once a suitable cell is found this cell shall be selected.
b) Stored Information Cell Selection
This procedure requires stored information of carrier frequencies and optionally also information on cell parameters, e.g. scrambling codes, from previously received measurement control information elements. Once the UE has found a suitable cell for the selected network the UE shall select it. If no suitable cell of the selected network is found, the Initial Cell Selection procedure shall be started.
However the initial cell procedure as set out in a) above requires that the UE only searches for the strongest cell for each carrier (i.e. frequency or frequency band). The UE then attempts to connect with the selected cell. If there is any problem with doing so, the UE then tries the cell which had the next strongest signal at another frequency. However this may not in reality be the next strongest signal.
There are thus proposed strategies for User Equipment (UE) measurement procedures, which are appropriate in idle mode and during cell selection in connected mode. A number of such strategies are detailed below.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of an apparatus and method for carrying out User Equipment (UE) procedures in idle mode and procedures for cell reselection in connected mode.
The same reference numerals are used in different figures to denote similar elements.